In wireless telecommunication systems, the design of data transmission is a challenging task. The data transmission may be impaired by several factors, such as fast and slow fading, multipath propagation, interference from other systems and interference from other users within the same system.
Several receiver algorithms have been designed to meet the challenges of wireless telecommunication systems. A receiver of a wireless system must be able to capture and demodulate the transmitted signal as efficiently as possible. Maximum Ratio Combining (MRC), Maximum Likelihood receiver and Maximum A Posteriori Receiver (MAP) are examples of known receiver algorithms.
For environments where interference is present, interference suppression methods have been developed. An example of such a method is Interference Rejection Combiner, which is an efficient method in applications where multiple transmission paths are utilized in the transmission of signals. An example of such utilization is the use of multiple antennas.
In general, to transmit signals of a multitude of users simultaneously, several channels are needed. In systems offering a large bandwidth to users, several channels may be offered to a single user. The channels may be realized with frequencies (frequency division multiple access), time slots (time division multiple access), codes (code division multiple access) and different combinations of the above. One example of an access method studied lately is single carrier frequency division multiple access, SC-FDMA. One promising variant of SC-FDMA is interleaved frequency division multiple access, IFDMA.
In the distributed type transmission, such as IFDMA, the signals of different users are orthogonal with respect to each other in frequency domain but interfere with each other in time domain. The present IRC algorithms, such as space-only IRC, space-time IRC, do not work efficiently in systems where the signals of different users are distributed among subcarriers.